1. Field of the Invention
The invention is related to making improvements in synthesizing homopolyamino acids or copolyamino acids.
b 2. Description of the Prior Art
Synthetic polyamino acids as protein model compounds are considered important as "biopolymers". Accordingly, applications in the industrial sector have become very active within the past years.
These synthetic amino acids have attracted attention as polymers for fixing useful bacterium and enzymes, carriers of fixing chemicals, special bonding materials, gas permeable membrane, antithrombus agents, foundation for cosmetics, skin covering materials, synthetic leather, ion exchange resins, chelating agents, foaming agents, fibers and various types of films.
Conventional methods of obtaining polyamino acids are given below. (1) The well known method of directly heating and polycondensing amino acids [Ann., 157, 24, (1871); J.C.S., 851 (1953); J.A.C.S., 80 , 3361 (1958); J.A.C.S., 80, 2694 (1958); J.A.C.S., 82, 3745 (1960)]. (2) Method of decarboxylation polymerization by using N-carboxyl acid anhydride (NCA) of amino acid [J.A.C.S., 79, 3961 (1957); J. Poly. Sci., A5, 2867 (1967); J. Poly. Sci., A14, 2065 (1976); Japanese Patent Publication Nos. 1967 (42)-20793 and 1971 (46)-27828]. (3) Method of polymerizing activated amino acid ester [Japanese Patent Public Disclosure (Laid-Open Publication) No. 1979 (54)-47799; J. Macromol, Sci. Chem., A15, 999 (1981); Khim, Prir. Soedin, 773, (1973)]. (4) Method of polymerizing N-dithiocarbonylalcoxylcarbonyl amino acid by heating [Japanese Patent Publication No. 1970 (45)-9391]. (5) Method of polymerizing acid chloride hydrochloride of amino acid (DOS 2364152).
However, obtaining polyamino acid by Method (1) aforementioned has disadvantages due to thermal decomposition of starting materials and formation of diketopiperazine, a byproduct formed by cyclization of dipeptide. Method (2) is widely used at present, but it has the disadvantage of using toxic phosgene in addition to problems brought about by the fact that NCA is unstable especially in relation to moisture and that it is difficult to manufacture the substances in large quntities. In methods mentioned above other than Method (1), the high production costs of the methods are prohibitive in terms of practical use.
The inventor has been successful in inventing a method of obtaining copolyamino acids [Japanese Patent Application No. 1984 (59)-60160] by mixing ammonium salts or amide of malic acid, fumaric acid and maleic acid with amino acid and heating the mixture in an oil bath to promote easy polycondensation.
Microwave is used widely in radar and other communication facilities and it is also making a major contribution in spectroscopy in the physical and chemical sectors. It is also used in household electronic ranges. However, microwave is rarely used for chemical reactions. Some of the typically rare examples are crosslinking polyurethane and plyester [RGE, Rev. Gen. Electr., 826, (1981)], polymerization of difluoroethylene [Eur. Polym., J., 15, 265, (1979)], manufacture of bonding agents [Japanese Patent Public Disclosure (Laid-Open Publication) No. 1978 (53)-109535], and manufacture of polyurethane foam (U.S. Pat. No. 3,294,879).
As mentioned above, there are disadvantages in the conventional methods of manufacturing polyamino acids such as unstable starting monomers, high prices, or complicated proceses. Furthermore, the method covered by Japanese Patent Application No. 1984 (59)-60160 is handicapped by requiring a comparatively long reaction time.